Can you confirm that if you tap in from a Zone 1 station going to Heathrow, but get off at Hatton Cross, tap out, and immediately tap back in, it’s cheaper than staying on the train?
Hatton Cross is (I think) now covered in the free fare zone around the airport and so it’s cheaper doing it that way! Yes, you have steps to climb to do it (leave a friend with your luggage) but I think this hack makes it quite a bit cheaper!